"The moral outrage directed toward those who engage in incest, homosexuality, bestiality, and so on is not a biological adaptation. Individuals who disapprove of these activities do not reproduce more than those who are indifferent, and societies with many such disapproving individuals are not more successful than those without them. Instead, this aspect of moral psychology is a biological accident. It just so happens that evolved systems that keep us away from parasites and poisons respond in a certain negative way to sexual activity. Over the course of history, this averse reaction has been reinforced, directed, and sanctified by various cultural practices, including religion and law."